Many coals contain up to about 30 weight percent of moisture. This moisture not only does not add to the fuel value of the coal, but also is relatively expensive to transport.
Consequently, many processes have been developed to dry coal. Illustrative of these processes is the one disclosed in U.S. Pat. No. 4,324,544 of Blake, in which coal is dried in a fluidized bed in which the heat necessary for drying is provided by partial combustion of the coal in the bed. By way of further illustration, U.S. Pat. No. 4,495,710 of Ottosan discloses a drying process in which particulate low rank coal is dried in a fluidized bed in which the coal is fluidized above a first portion of a gas flow distributor using a hot fluidizing gas, and also above a second portion of the gas flow distributor using a recycle gas stream at a temperature less than about 200 degrees Fahrenheit. The disclosure of each of these United States patents is hereby incorporated by reference into this specification.
The coal produced by the processes of the Blake and Ottosan patents suffers from two major disadvantages. In the first place, the drying process is reversible, and when the coal is allowed to stand in the presence of a moisture-laden atmosphere, it regains some or all of its initial water content. In the second place, the coal is often likely to undergo spontaneous combustion upon standing in air.
It is an object of this invention to provide a process for irreversibly removing moisture from coal which does not require substantial amounts of externally provided energy to drive it.
It is another object of this invention to provide a process for producing coal which is not likely to undergo spontaneous combustion.
It is yet another object of this invention to provide a process for comminuting coal without using mechanical grinding means.
It is yet another object of this invention to provide a coal which, even after it is stored under ambient conditions for prolonged periods of time, has a relatively high heating value.
It is yet another object of this invention to provide a novel coal-water slurry.